10 Easy Steps…….

May 30, 2013

…….To Efficient Irrigation Design

It’s the 30th of May, 2013 and we’ve probably had our last rain of the season, now for the long dry California summer to settle in on us. We’ve topped out here in Applegate with about 32.90 inches of rain since last July first. With water rates going up now is the perfect time to review existing and proposed irrigation systems and make sure you’re using your water as efficiently as possible. And so with that in mind I’ve created a punch-list of 10 easy steps to achieving this goal. Some of this stuff is, what I would call, a “no-brainer” but drive around town and chances are there will be plenty of examples of the “no–brainer” being either the installing contractor, the gardener or the homeowner and how they mismanage the water system.

Step 1. Know your soil.What’s its texture? What is it’s water-holding capacity? What’s its organic matter content? What’s its infiltration rate? These are crucial parts of the puzzle when it comes to selecting an application method and run time. A couple of ways to determine texture. 1) do a jar test. Take some representative samples of the soil down about 6 – 8 inches and plop it in a mason or peanut butter jar. Add water and shake. Let it settle. The sand will settle out in a couple of minutes or less; the silt will settle out over the next couple of hours and the clay will take about 24 hours give or take a bit. Some will stay in suspension indefinitely. Now, measure the total depth of the sample and then the depth of the individual layers of sand, silt and clay. Determine the % of each layer by dividing the layer depth by the total depth. Google “Soil Triangle” and print out one that looks good to your eye. In most cases you’ll be able to determine your soil texture from this simple test. 2) This second way is to take this same original sample and, rather than doing your own test, send it off to a soil testing lab. For around $30 – $80 (prices will vary depending on the extent of the testing) you’ll get loads of information on texture, infiltration rates, fertility and you can get the labs comments/recommendations on improving your soil.

Step 2. Know Your Site.What is your daily/monthly/yearly ET rate? Which direction does your garden face – North, South, East or West? All 4? Any micro-climates that need to be considered? Again, these are elements that will come into play – especially your ET (evapotranspiration) rate. This information is readily available through State or University websites. In California we have CIMIS – California Irrigation Management Information Service. You sign up for it on-line, it’s free and it gives you tons of weather data for your location. The aspect (direction) of the garden tells you how much, or little, sun may hit and that will affect applications methods and sprinkler run times.

Step 3. Develop a Plan.OK, this is one of those “no-brainers” I spoke of earlier, but think about it. How many times have any of us (and certainly homeowner DIYers) run down to the nursery and bought one of every plant available with no idea of where they’re going to be planted or what their individual requirements are? The plan doesn’t have to be super sophisticated, but it should at least give an idea of what the garden will eventually look like. This is where a little research will go a long way. Group plants together based on water requirements as much as on aesthetics and purpose. A plan can be a simple as a bunch of free-form shapes labeled with Low, Medium and High referring to the water use of the plants that will be in that region. This starts to set the stage for proper zoning of the irrigation system and, consequently, efficient use of the water. Not sure of what the water use is for a selected plant? For California we have the Water Use Classification Of Landscape Species (WUCOLS) to use. Again, Google it. Currently it’s being revised, updated and expanded. If you don’t have anything like this where you live talk to your local nursery or garden center (find one where the employees actually know something!).

Step 4. Know Your Water Source.How much water you have available to use is pretty critical as to how many valves you may end up needing to use. If you’re on a meter then what size is it? The size should be stamped on the meter itself – 5/8″; 3/4″ etc. If you’re in Canada or Europe then maybe it’s metric, doesn’t matter. You can only push so much water through a meter and your local water agency or utility will help you to determine that flow rate. Let’s say you’ve got a 5/8″ meter. Well, it has a flow capacity of 20 gallons per minute (gpm) but realistically and from a safety standpoint you should only push 75% of the capacity through the meter. So a 5/8″ meter would provide 15 gpm. This same criteria should be applied if your water source is a private well. If your well puts out 12 gpm then design your system to use no more than 9 gpm – this leaves some for the house and for any possible fluctuation in the flow capacity of the well.

Step 5. Spray the Lawn; Drip the Shrubs.Drip, or micro, irrigation is much more efficient than spray and shrubs tend to block the spray pattern on sprinklers. Don’t use “Leaky Pipe” (that spongy hose tube stuff) unless you aren’t interested in watering efficiently. Most turf is a High Water Use plant – keep this in mind when designing a water-efficient landscape. So this is a pretty straight-forward statement and the thing is, it works.

Step 6. Give The Plants The Water They Need and No More.So how much water do your plants need? That’s going to depend on some factors. 1)Are they low, medium or high water use? this information is available through WUCOLS or your local garden center. 2)What is the climate they are growing in? (a Ceanothus growing on the coast will require less water than one growing in our hot inland valleys). But it’s not just the climate, find out what the ET rate is for your area. As water evaporates from the soil and the plant the available water in the soil is depleted. This is what needs to be replaced to help keep your plants healthy. The ET rate will vary throughout the year and so will the water needs of the plant. Your local agricultural extension should have this information or use CIMIS. 3)How deep do the plant roots go? If your plants roots grow 12 inches into the soil then there isn’t much reason to irrigate long enough that the water percolates down to 18″ or more – the plant can’t use it and so in essence it’s being wasted and that’s not efficient. 4)How fast does the water soak into the soil? Knowing how fast the water infiltrates the soil will tell you how long to let the water run in order to get the moisture into the root zone. Many controllers now have a “Cycle and Soak” feature that allows you to run the water for a short time, let it soak in and then water again and this helps to prevent run-off. Use a soil probe to see how fast and deep the water moves.

Step 7. Mulch.Pure and simple; 2 – 4 inches of mulch saves water and moderates the temperature of the soil keeping roots cool. Know your plants! Some plants like organic mulch while others, like lavender and dianthus, like gravel or decomposed granite.

Step 8. Install a Smart Controller.Every manufacturer of irrigation equipment has this style of controller. How much do they cost? (there’s a saying in racing – “speed costs money – How fast do you want to go?”) Check with your local irrigation supplier and have them explain the different options and features.

Step 9. Monitor Your System.Even the best designed system needs to be watched. Don’t just set it and forget it because if something can go wrong it will. Walk around once in a while and watch how everything is working, that there are no leaks or breaks in the system and if there is a problem repair it as soon as possible.

This is my backyard. It’s pretty much the last bit on our 1.7 acres that needs a new design. So, over the next month or two I’ll be documenting the transformation of this small bit of ground from the lawn as it is now to a new, water-efficient landscape. I’ll be getting progress photos from these locations throughout the project. I took these a bit early in the day – the next set will be better.

My goal: Create a native plant, low water use garden with places to sit. Plants that are food sources for butterflies and bees as well as have the host plants needed for butterfly and moth caterpillars. Eliminate all lawn. Provide water and feeding stations for birds. Convert from spray irrigation to drip. Do all of this organically – no herbicides or pesticides allowed. A couple of butterflies I want to attract are the anise swallowtail (larvae on fennel in my garden) and the Pipevine Swallowtail (larvae on a pipevine in the American River canyon)

Rob Littlepage is a landscape architect, designer and Founder/Director of the California School of Garden Design, located in Applegate, Calif. He studied design at the Oxford College of Garden Design in England under Duncan Heather - one of Europe's foremost garden designers. He travels extensively throughout the American West, Mexico, Scotland and England preferring the wild country to cities. He is also a builder and player of custom, open-back banjos.